Amplifier circuits



Dec. 11, 1945. BRlNTON I 2,390,773

AMPLIFIER CIRCUITS Filed July 3, 1943 I a g 3% 4 5% MAIN INPUT I ovrPu-r TO TERMINALS ELECTRO RESPONSIV: E 7 I DEVICE.

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J J I/ AUXILIARY AMPLIFIER. AUXILIARY AMPunE RATIO M. RATIO M.

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AMPLIFIER.

Inventor: Howard G. Brh ton,

His Attorney.

* NITED STATES- PATENT OFFICE AMPLIFIER CIRCUITS Howard G. Brintcn, Plttslleld, Masa, asslgnor to General Electric Company, a corporation of New York Application July 3, 194:, Serial No. 493,335

11 Claims. (Cl. 179171) plifier, as contrasted with a linear amplifier in which the ratio of the input to the output is constant.

The invention utilizes as its principal element a varistor which is a resistor having such a pronounced non-linear volt-ampere characteristic that practical use may be made of it. In par ticular it uses a ceramic varistor made in accordance with Patent 1,822,742, granted September 8, 1931 on an application of K. B. McEachron and assigned to the assignee of the present application. This material is manufactured by applicant's assignee under the name of Thyrite. The characteristic of this material is usually delined by the fundamental equation Ir=C. In this equation I is the instantaneous value of current through the resistor in amperes, r is its instantaneous resistance in ohms, C is its resistance in ohms when the current through it is one am pere and this is determined principally by the value the amplifier would have an infinite percentage change amplification. As varistors are rugged, static and stable devices and as Thyrite is substantially instantaneous in action, a percentage change amplifier utilizing the properties oi such material will also be a rugged, fast, static and stable device.

An object of the invention is to provide a new and improved amplifier system.

Another object of the invention is to provide a high percentage change amplifier system which Y is rugged, fast, static and stable.

t The invention will be better understood from the iollowing description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

In the drawing Fig. 1 illustrates diagraminatically a multi-stage embodiment of the invention utilizing feed back and an auxiliary amplifier to produce increased percentage change amplification, Fig. 2 is similar to Fig. 1 but does not have feed back, Fig; 3 is a modification utilizing transformers between stages which is particularly suitable for altemating-current applications, Fig. 4 is another modification suitable for direct current in which the stages of the amplifier are coupled through high-speed dynamo-electric amplifiers, Fig. 5 is a modification in which separate terminals are provided for input power and the input signal, Fig. 6 is a modification of Fig. 5, and Fig. 7 is anothermodification of Fig. 5.

Referring now to the drawing and more particularly to Fig. 1, the amplifier system is pro-.

vided with a pair of main input terminals I across which the input voltage E is impressed. serially connected in a circuit across these input terminals i is a non-linear resistor 2 and a second resistor 3.. The voltage across a part or all of the resistor 3 is the output voltage of the first stage of the amplifier and consequently the second stage input terminals will correspond to the first stage output terminals. The second stage is similar to the first and consists of another non-linear resistor 4 and a resistor 5 serially connected in a circuit across the resistor 3. Aithough only two stages have been shown,

it will be obvious that as many similar stages as desired may be employed. The main output the iast stage.

In order to improve the operation of the re- I sister by either increasing its percentage change amplification ,or by increasing the output voltage an auxiliary amplifier 6 of any suitable and well-known type may have its output terminals connected in circuit with resistors 2 and 3 and have its input, terminals connected to respond to the voltage drop in resistor 3, and a similar amplifier i may have its output terminals connected in circuit with the resistors 4 and I and have its input terminals respond to the voltage drop across resistor 5.

Resistors 2 and .4 are preferably of the type whose resistance current characteristic is defined by the previously-mentioned equation I"1'=C. In some cases it is more convenient to convert this equation into one which defines r in terms of I, a and 0, this latter equation being r=CI-.

The operation of Fig. 1 is as follows: Neglecting for the time being the auxiliary feed back controlled ampllflws and l lam ohmic values of reslstms small ln comparison with film @lamls J 3 (which, of coursals alas; my '2) mil be approximately al s0 for the same'vallla a as 510ml lo the 12.25 power m the nutpul voltaga m the pmporllonal to the l lllm 13mm ill pm'tiuml lo the 153ml M maul voltage the flllll mllplal walla small l.

* the mltplli' ml 13 or $3 wllll stages. lnczcease ln the mllpul; ml lay a maxim M91 when l mall value of input millage l'iillTGE' 1% imarealseo This aamplifylng @fiecl lat; by Zllfil?l1g rasislor 8 m: m material that its rent increases, Fm" em J37 stem lamp filaments me Eli-ll ha ballast treslslurs.

' Gmsltlefing now film, a-sllem @L'f wmrlllled amiillzwy ampllfi film-i. 'llley have empllfimllm rs" suma further that Z is the lsnaajl the first stage setween me mam will exclusive of the reslsllmce i @2? Then the voltage drag in the zeslslfil 2 which ls squall lo 61 plus lhe wllaga ill 'llw lm pedlmce of the rest'uf the (2& will we equm to E plus the output Wltaga @l the am lllal'y amplifier 5 which will ll SlglllEl-l 's-il lls ln pull. veltage or RI, ln "whlm is res' fimmfi of resistor 3, times l :5 falls ll; @2 ml: lecting: the terms in l lhla Gilllil'lillllll may lmwrl'l tsn m simplified form as E W -K1 in. which K (MR- 2} I x I have found that this lair-mall wlll gamslmw the maximum possible percentage small Emmi flnaflon if K is equal to lllm mllwm 82ml wmpm's tlwly small 3 ill anal we mt m cessam in was? to ll para; the current away 13mm resislr output 01' Km" secoml stage.

ll We: l'la'vae been shown in Fig. 1 a stage alone may be mail 01' as many all @dtll 1'1 as deslrezl may be :he lead 90:16am}, amplifications 6 an 1 have hem arml'l'uecl stages I] and 2 g is illitllglll; reslstanca sampling be K l anal 3.1141 mtweml stages 2 1-]. wl llt-lon m1 amplifier 05 any sulta 9 small a, vacuum "tube amplifier imserlsll in the third stage so as to the amplifier 3 is cenmalsml' amplifier reslfima: 1 and relmllzlr reslsmrs l 2 Warm be fi m/mus fmm us llescl'l'gsllm 3f l,

slams are sampled by c2 3, and l0 1 'l-lll fillcllll] l5 33333] sull 1 mm, Whereas "slla 3i? l with ellzllel' altermlt m @f slaw llls eutput any lla-sllell all lgllml by l-llgllwpeecl jpllflers l3, 65 am clalmell in Edwards me known sa lll ifilllllfis dimes aml '533'357 am 3?:

msltallom gamma-cell by Talia? wall 11% a mm l, 5 3 331F311 7310552; ls

l the vglaze @gsemtlml @l isllls slrcull; me zmmllmezlr realslmm G and Q cause the voltaga mamas the central field wlnillngs ll, EH3 and all m increase at a gamma: rate than the input Wfltllge to their resgzesllw images and the Qullput voltages of the mmmlurw @23 the machines 35), El; and 58 bein very mml larger than the voltages llcrcess thelr cmlml wlmlmgs will pmduce a further @fifill.

A @lwlmmly, it ls ml necessary to have m many ampllalynm as were are stages and some a! the may he slmlght mslstamce coupled or lll-w may have lead back amplifiers asln Fig. 1.

. 1n 5 an lmulating transformer 259 is conmlssl ed between the main input terminals and the filial stage and mother pair of input termimall; la wzmeeted t0 supply energy to the first mil 3369 mm alarmist the nan-linear resistor 2 and the primal windlng @f the voltage step-up transformer M. This circuit is completed through l'eslata l's 22 and 23 wlhlch are in the circuits of lhe mlmiad marl llllrd atages respectively an that 86 warm-lam in voltage between the input terminals l is up we ill-2 drop in wlmge through thesignal and input terminals 2| may be connected 6 to a source of relatively large power or these terminals may be'interchanged so that 2| receives the control signal and terminals l are energized by the source of control power or both may receive variable control'signals. l

In Fig. 6 three 'difl'erentcontrol signals may be mixed by applying one of them to terminals I and the remaining two to terminals 23 and 24 respectively, which latter two terminals are in the second and third stages. 16

Fig, '7 is similar to Fig. except that the resistors 22 and 23 have been omitted so that variations in voltage between input terminals 2| are only applied directly in the circuit or the first stage which includes the non-linear resistor 2. 2

While there have. been shown and described particular embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications can be made therein without departing from the invention and, there- 25 fore, it is aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim 'as new and desire to secure'by Letters Patent of the United States is:

1. In an amplifier system of the type having a source of variable voltage, a pair ofvo'utput terminals, and means for impressing a voltage across said outputterminals which varies when the voltage of said source varies but by a much greater percentage, thecombination of an impedance connected in circuit with said source of variable voltage, said impedance having a non-linear volt-ampere characteristic expressed by the across it, C is its ohmic impedance when carrying one ampere and a is less than 1, a linear impedance connected in series with 'said non-linear impedance, the value or said linear impedance being so much smaller than the value of said nonlinear impedance that substantially all or the voltage of said source of variable voltage is across said non-linear impedance throughout the entire range of variation oi said voltage, a second non-linear impedance similar to the first one, means for connecting said second non linear im- ,pedance in a circuit whose voltage is proportional to the current in the said linear impedance, a second linear impedance connected in series with said second non-linear impedance, the value of said second linear impedance being so much smaller than the value of said second non-linear impedance that substantially all or thevoltage oi the first linear impedance is across said second non-linear impedance throughout the entire range of variation of said voltage, means for obtaining a voltage which is responsive to the current in said second linear impedance, and means tor impressing said last-mentioned voltage across said output terminals,

2. A' simple. lled. fast, static, stable high percentage change amplifier comprising, in combination, a pair of input terminals, a pair oi output terminals, a lurality of varistors whole II volt-ampere characteristics are defined equation where I is the amperes through them, E is the voltage across them, C their ohms with one ampere through them and a is between 0 and 1, means for connecting one of said varistors in a circuit across said input terminals, means including separate impedors in series with saidvaristors for developing separate voltages proportional to the current in each of said varistorsrespectively, said impedors having ohmic values which are very much smaller than the ohmic values of said varistors throughout the entire resistance variation range of the latter, and means i'orconnecting said output terminals across the voltage developing means which is responsive to the current in another of said varistors, and means iorconnecting said other varistor in a circuit which is responsive to the voltage developing means which by the is associated with the varistor which is connected in circuit with said input terminals,

3. A multi-stage percentage change'amplifler comprising, in combination, a pair of input terminals,'a pair of resistors connected in series between said terminals; one of said resistors having a non-linear volt-ampere characteristic which is defined by the equation i 1o where I is the amperes through it, E is the volts across it, C is its ohms with one ampere through it, and a is more than 0 and less than 1, a second pair of resistors connected in series across the V other resistor 01 the first pair, one of the resistors equation I e 40 of the second pair also having a non-linear voltampere characteristic which is defined by the equation L 1-a e and a pair 01' output terminals connected to be responsiveto the voltage across the other of the resistors of the second pair, said other resistors being linear and having ohmic values which are very much less than the ohmic values of said non-linear resistors throughout the entire resistance variation range of the latter.

4. A multi-stage percentage change amplifier comprising. in combination, a pair of input terminals, a pair of resistors connected in series between said terminals, one of said resistors having a non-linear volt-ampere characteristic which is defined by the equation pair of resistors connected in series across the other resistor of the first pair, one or the resistors of the second pair also having a non-ii ear voltampere characteristic which is defined by the equation L j 1-1! v Hg), and a pair oi output terminals-connectedtobe sistors having a positive resistance current char acteristic.

5. A multi-stagc percentage change amplifier comprising, in combination, a, pair of input ter minals, a pair of resistors connected in series between said terminals, one of said resistors having a non-linear volt-ampere characteristic which-is defined by the equation where I is the amperes through it, E is the volts across it, C is its ohms with one ampere through it, and a is more than and less than 1, the value or the other of said resistors being so much smaller than the value of said non-linear resistor that substantially all of the voltage between said input terminals is across said non-linear resistor throughout the entire range of variation of said voltage, a second pair of resistors connected in series across the other resistor of the first pair, one of the resistors of the second pair also having a non-linear volt-ampere characteristic which is defined by the equation the'value of the other resistor o! the second pair of resistors being so much smaller than the value of the non-linear resistor 01 the second pair that substantially all of the voltage across the other resistor of the first air is across the non-linear resistor of the second pair, a pair of output terminals connected to be responsive to the voltage across the other or the resistors of the second pair,and means for boosting the voltage across said output terminals.

6. A multi-stage non-linear amplifier comprising, in, combination, a plurality of voltage step-up transformers in which the primary winding of each one except the first isconnected in circuit with the secondary winding of a different one, an equal number of resistors each having a volt-ampere characteristic defined by the equation where I is the amperes through it, E is the volts 7 comprising; in combination, a pair olmain am-.

plifier input terminals, a pair, of resistors, an auxiliary linear amplifier having an amplification ratio M, said resistors and the output of said auxiliary amplifier being connected in'series between said main input terminals, one of said re-.

sisters having a current dependent ohmic value *equal to 61- where C is its ohms at one ampere through it, I is the amperes through it and a is greater than 0 and less than 1, theother of said resistors having a substantially constant ohmic voice It, and a pair oi main amplifier output tier minals, said main amplifier output terminals and the input of said auxiliary amplifier being connected to respond to the voltage drop across said other resistor, the total impedance between said main amplifier input terminals exclusive of said current dependent resistance being Z,

MR-Z

being substantially equal to I a l 8. In combination, a pair or input terminals, apair of output terminals, a plurality of non-linear resistors which have a volt-ampere characteristic defined by the equation 4 where I is the amperes through it, E is the volts ohmic values including a plurality. of linear resistors whose ohmic values are very much smaller than the of said non-linear resistors throughout-the entire resistance variation range of the latter for connecting said non-liriear.re--

sistors between said pairs of terminals in cascade circuit relationship so that the voltage across the pair of output terminals will vary as the 'power of the per unit value of the voltage across the pair of input terminals where nis the number of cascaded steps. 9. An amplifier having a stage comprlsnig, an

input circuit and an output circuit, an amplidyne generator having an armature connected in said output circuit, a non-linear resistor having an ohmic value equal to 01" where C is its ohms'at input circuit and an output circuit, an amplidync generator having an armature connected in said output circuit and a. control field winding connected in said input circuit, and a. non-linear re.-

sistor whose ohmic value decreases with increases in current through it connected in said input 11. An electric translating system comprising, an input circuit and an output circuit, on amplidyne generator having an armature connected in said output circuit and a control field winding connected in said input circuit, a. non-linear resistor connected in said input circuit, the minimum operating resistance of said non-linear resistor throughout the range of operation of said translating system beingsuch that substantially all of the input circuit voltage is across it.

HOWARD G. 'BBINTON. 

